1. Technical Field
The present disclosure relates to an electric caliper brake, and more particularly, to an electric caliper brake capable of simplifying a structure and improving operating efficiency.
2. Description of the Related Art
In general, an electric caliper brake is a device obtained by incorporating conventional hydraulic disk brakes into actuators that are electrically operated.
Korean Patent Publication No. 10-2011-0124817 discloses an example of such an electric disk brake (hereinafter, referred to as an electric caliper brake). According to the disclosed document, the electric caliper brake includes a disk rotating together with a wheel of the vehicle, a carrier provided with a pair of pad plates for pressing the disk so as to be able to move forward and backward, a caliper housing slidably installed on the carrier and provided with a cylinder in which a piston can be advanced and retracted by braking hydraulic pressure, a spindle pressing the piston, and a motor and a speed reducer for an actuator for transmitting a rotational force to the spindle.
The electric caliper brake performs a parking function by applying a braking action by pressing the piston according to the braking hydraulic pressure, or by receiving a rotational force generated from the motor and pressing the piston by a spindle which converts rotational motion into linear motion.
Meanwhile, the electric caliper brake is normally required to be provided on the piston in a state in which the rotation of the spindle is restricted in order to convert the rotational force of the motor into a linear motion. For this purpose, since a head portion of the conventional spindle, which presses the piston, has a protrusion portion for restricting the rotation, the weight of the spindle increases. In particular, since the conventional spindle is formed of a steel material, the increased weight exerts a large load on the caliper housing, adversely affecting the fuel economy of the vehicle. Further, since the protrusion portion must be formed through a cutting process, there is a problem that processing is difficult.
In addition, in the conventional electric caliper brake, the stroke (pedal travel distance) of the brake pedal is varied according to the required fluid amount of the brake oil transmitted to the cylinder during a braking operation. For example, in order to improve the braking feeling during a braking operation, the required fluid amount of the brake oil must be reduced. However, in the conventional electric caliper brake, there is a predetermined space between the piston and the spindle, for example, in a cylinder receiving a braking oil pressure, which increases the required amount of brake oil for braking, thereby reducing the feeling of braking.
The spindle of the conventional electric caliper brake also includes a nut member and a spindle member that are screwed together to press the piston. The nut member contacts the piston and the spindle member is coupled to the motor so that the rotational force of the motor is transmitted to the piston.
More specifically, when power is applied to the motor, the spindle member rotates in the forward/reverse direction to move the nut member forward and backward. At this time, a stuck occurs when the nut member is excessively close to the spindle member. This problem is caused by the retraction of the nut member up to the threaded portion of the spindle member or by the clearance or wear of the manufacturing process. To prevent this, a stopper is provided on the opposite surface of the spindle member and the nut member and blocks over-release of the nut member. However, occasionally, the stopper does not operate normally when the thread dimension is unstable or the stopper is damaged due to abrasion or impact.    (Patent Document 1) Patent Laid-Open Publication No. 10-2011-0124817 (2011 Nov. 18)    (Patent Document 2) Patent Registered No. 10-1220294 (2013 Jan. 3)